Human subject testing will involve a cross-sectional, repeated measures study consisting of a single 3 hour visit wherein participants will initially stand and then continuously walk at their self-selected speed for ten minutes on a level treadmill with the prototype under two randomly presented conditions of the mechanical system: 1) fully functional, and 2) locked to restrict axial displacement. After written informed consent is obtained, information on socket comfort and mobility capability will be collected. A load-cell will be installed proximal to the prototype and in-line with the prosthesis to measure instantaneous socket-reaction moments.